1. Field of the Invention
The invention relates to a semiconductor light-emitting device and method of fabricating the same, and more particularly, to a ZnO-based semiconductor light-emitting device and method of fabricating the same.
2. Description of the Prior Art
Light-emitting diodes (LEDs) are semiconductor devices initially used for indicator lamps or display panels. As the emergence of white light LEDs, LEDs can also be used for illumination. Comparing with traditional light sources, LEDs have the advantages of high efficiency, long lifetime, high durability and high reliability, etc. It is renowned as revolutionary light source of the 21st century.
Zinc oxide (ZnO) is a II-VI group compound semiconductor with a direct bandgap energy of 3.37 eV at room temperature, and its emitted light is in the range of ultraviolet.
As a raw material for fabricating white light LEDs, the zinc oxide has following advantages:
1. Abundance and relatively low cost of raw materials.
2. The exciton binding energy of zinc oxide is up to 60 meV, so the light emitting efficiency is high.
3. Since the emission wavelength of zinc oxide is around 380 nm, it is more efficient in exciting fluorescent material than other materials (e.g. GaN) for fabricating white light LEDs. Therefore, the zinc oxide is very suitable for fabricating white light LEDs.
4. Zinc oxide is easier to be processed by chemical etching than other materials (e.g. GaN) for fabricating white light LEDs.
However, zinc oxide shows intrinsic n-type characteristics due to the presence of native defects, such as oxygen vacancies and zinc interstitials. Thus it suffers from the difficulty to prepare reliable and high-quality p-type zinc oxide. In order to realize a high-quality p-type zinc oxide, high-concentration p-type doping is needed to overcome the strong self-compensation effect resulting from the native n-type defects. Nevertheless, the solid solubility of p-type acceptors in zinc oxide is not high enough to achieve high p-type doping concentrations. Therefore, it is difficult to produce high-quality p-type zinc oxide, as well as the important structure of an LED, the p-n junction. As a result, a reliable growth technique is desired for the growth of high-quality zinc oxide.
Though zinc oxide is suitable for fabricating a white light LED, but owing to the limitations described above, the technology of fabricating a white light LED with zinc oxide is held up.
Accordingly, a scope of the invention is to provide a zinc-oxide-based semiconductor light-emitting device and a method of fabricating the same to solve aforesaid problems.